#include <iostream>
#include <cstring>

using namespace std;

const int N = 510, INF = 0x3f3f3f3f;

int d[N][N];
int dist[N];
bool st[N];
int n, m;

int prim()
{
    memset(dist, 0x3f, sizeof dist);

    int res = 0;
    for (int i = 0; i < n; i++)
    {
        int t = -1;
        for (int j = 1; j <= n; j++)
            if (!st[j] && (t == -1 || dist[t] > dist[j]))
                t = j;

        if (i && dist[t] == INF) return INF;

        if (i) res += dist[t];
        st[t] = true;

        for (int j = 1; j <= n; j++) dist[j] = min(dist[j], d[t][j]);
    }

    return res;
}

int main()
{
    scanf("%d%d", &n, &m);

    memset(d, 0x3f, sizeof d);

    while (m--)
    {
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);
        d[a][b] = d[b][a] = min(d[a][b], c);
    }

    int t = prim();

    if (t == INF) puts("impossible");
    else printf("%d\n", t);

    return 0;
}